User Manual

doepfer

System A - 100

Ext. Input / Envelope Follower

A-119

3. The Envelope Follower: how it works

The external audio signal (see Fig. 1a) is patched into

input

, depending on its level. It is amplified by

an amount set by the gain control

, brought up to

A-100 internal operating level, and can then be output

from audio outs

and/or

To produce envelope and gate signals, the amplified

signal is put through a full-wave rectifier, so that the

internal signal output has only positive voltages (see

Fig. 1b).

Next, the rectified signal passes through a 50 Hz low

pass filter, and is sent to envelope output

H With input frequencies of less than 50 Hz,

patch the envelope output % into an A-170

slew limiter, set to a time constant of greater

than 20 ms, to avoid remnants of the signal

being audible in the envelope.

The signal at the envelope output is compa-

red with the adjustable trigger threshold (T in

Fig. 1c), to produce gate signals, available at

output

Fig. 1

: The envelope follower: how it works